[hinkley]

When we were upgrading to ES6 I was surprised/relieved to find that moving some leaf node code in the call graph to classes from prototypes did help. The common wisdom at the time was that classes were still relatively expensive. But they force strict, which we were using inconsistently, and they flatten the object representation (I discovered these issues in the heap dump, rather than the flame graph). Reducing memory pressure can overcome the cost of otherwise suboptimal code.

OpenTelemetry having not been invented yet, someone implemented server side HAR reports and the data collection on that was a substantial bottleneck. Particularly the original implementation.